Performance of Reyhanlı Dam during February 6, 2023 Kahramanmaraş-Türkiye earthquake sequence

The February 6, 2023 Türkiye-Kahramanmaraş earthquake sequence subjected Reyhanlı Dam to strong near-source ground motions. The dam is located in Hatay-Reyhanlı district of Türkiye, 23.2 km away from the fault rupture plane of the Kahramanmaraş-Pazarcık M7.8 event. The peak ground acceleration at comparable distances from the fault ruptures was estimated to vary in the range 0.1–0.4 g and 0.02–0.04 g, during Pazarcık and Ekinözü-Elbistan events. Consistently the peak ground rock acceleration at the dam site is governed by Pazarcık event, and estimated as 0.3 g. The permanent total ground deformations, in terms of lateral and vertical displacements were mapped at the crest and reported to vary in the range of 10–30 cm, and 100–120 cm, respectively. No surface manifestation of soil liquefaction was observed at the dam body, or at its foundation soils. As part of preliminary reconnaissance assessments, limit equilibrium-based slope stability and simplified permanent deformation assessments were performed to evaluate the conformity of the predicted and observed responses. In between KM: 0+900 to 2+000 the permanent displacements consistently increase with increasing the transverse section height of the dam. Bray and Travasarou (2007) [20] semi-empirical simplified method produced the most consistent predictions for both the upstream and downstream slopes. In between KM: 6+000–8+120, large displacements were observed, higher than the values predicted by all methods, but in better conformance with the ones of Makdisi and Seed (1979) [15]. The increased permanent displacements were attributed to the presence of sand lenses in the foundation, which might have been cyclically softened, or even cyclically liquefied during the Pazarcık event.